Lymph node metastasis and cell movement: ultrastructural studies on the rat 13762 mammary carcinoma and Walker carcinoma

The aim of this study was to determine whether tumor cells move actively through the linings of lymph node sinuses. Using 13762 carcinoma in F344 rats, and Walker carcinoma in Wistar rats, 20 X 10(6) tumor cells were injected into the footpad, and the ipsilateral popliteal lymph node examined by transmission electron microscopy. The same tumors were examined by making standard cell spots on plastic or glass surfaces, and examining these by phase and reflection contrast microscopy, fluorescent microscopy after anti-actin and phallacidin staining and transmission electron microscopy. The 13762 cells do not migrate through the lining of the lymph node sinusoid, nor move actively in vitro. Ultrastructural appearances of the Walker rat carcinoma cells suggest that they move actively through the sinus lining. After 24 h in vitro the Walker rat carcinoma cells in the centre of the spot are adherent to the surface. There is some movement of the edge of the sheet, and individual tumor cells at the edge of the sheet move actively and independently. We conclude that the Walker rat carcinoma invades the lining of the lymph node sinusoid by active cell movement, and the 13762 carcinoma does not.